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The case interview: "How would you spend this budget?"
7 minutes, 9 steps, workout 4 of 6 in this module
The interview has gone well for forty minutes, then the hiring manager slides a sheet across the table: here is a monthly ad budget, how would you spend it? Many candidates lose the offer right here, not for lack of ideas but because they blurt out a split they cannot defend once the follow-up questions start. Teams ask it because it is the job in miniature: limited money, incomplete data and someone waiting for a reasoned answer. That reasoning can be practiced before you are in the room.
What you'll be able to do
By the end of this workout, you'll be able to work through a budget-split case out loud: clarify the goal, estimate cost per order by channel, propose a split, state the expected result and name the risks.
A first look: The five moves of a budget case
Every budget case follows the same five moves. One: clarify the goal and the constraint (what result, at what cost, by when). Two: lay out the options, usually channels, and what you know about each. Three: put numbers on them; expected cost per order is the key one, and it's just cost per click divided by conversion rate. Four: propose a split and say what result you expect from it. Five: name the risks and what you'd test first. Say the moves out loud as you go: “First I want to be clear on the goal...”. The interviewer isn't grading the final split; she's grading whether you can get there with reasons. Be careful with the first number you say: it anchors the whole conversation, both for you and for the interviewer. Say numbers when you've earned them from the data, not before.
Example: “Before I split anything: is the goal orders at a target cost, or growth in new customers? And do we have last quarter's cost per click and conversion rate by channel?”
What this workout covers
- 1The five moves of a budget case
- 2Case: The Northpack case: the data
- 3Case: Proposing the split
A question from this workout: The Northpack case: the data
Interviewer: “Good questions. The goal is orders at $40 or less per order. Here's what we know from last quarter. Search demand is limited: past about $8,000 a month, Search cost per click climbs fast.”
- Monthly budget
- $20,000
- Target cost per order
- $40 or less
- Google Search
- $1.20 per click, 3.0% conversion, demand caps near $8,000/month
- Meta Advantage+
- $0.60 per click, 1.2% conversion
- TikTok
- $0.40 per click, 0.5% conversion
Before you split anything, what's the first thing you compute?
- Which channel has the cheapest click; that's where the money goes
- Expected cost per order for each channel: cost per click ÷ conversion rate
- Total possible clicks if the whole budget went to one channel
- The average of the three conversion rates
Pick your answer first, then open the reasoning below.
Show the answer and the reasoning
Answer: B. Expected cost per order for each channel: cost per click ÷ conversion rate
The goal is stated in cost per order, so you convert every channel into that unit first. Cheap clicks with a low conversion rate can be the most expensive orders. The most common mistake is picking the cheapest click. TikTok's $0.40 click looks great until you divide by 0.5%.
The other steps work the same way: you decide first, then see why each option is right or wrong.
How you practice here
- 1 short concept card
- 2 multiple-choice questions
- 2 campaign cases with real-looking numbers
- 1 put-in-order exercise
- 2 guided calculations
- 1 recall question from an earlier workout